Skip to main content

Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

See other formats


GLACIERS OF PASSAGE CANAL AND BLACKSTONE BAY        361
with the position and trend of the terminal moraine to the east of this island, has been regarded, both by Grant and Higgins and by the junior author, not as a feature related either to climate or soil, but as clear proof of a maximum of the Blackstone, Beloit, and adjacent glaciers a century or two ago. Whether this followed a long period of glacial retreat during which the thick forest advanced to the very head of Blackstone Bay is unknown. This maximum may have been as recently as 116 years ago, for Whid-bey's map made in 1794 shows Blackstone Bay much shorter ("two leagues and a half" in length) than in 1910, though it is not detailed enough for us to be sure of the conditions; and, as usual in Vancouver's maps, no glaciers are shown. Willard Island is not indicated at all in the 1794 map.
The barren zones around the termini of Tebenkof, Ripon, Lawrence and other glaciers (bb, Fig. 58), with their youthful shrubs, attest to a more recent period of glacial change. As already pointed out, this was double in the case of Tebenkof Glacier, whose terminal moraines have shrubs 12 and 18 years old respectively, and perhaps double in the case of Ripon Glacier, in whose barren zone there appear to be moraines and shrubs of two ages.
PASSAGE CANAL
General Description. Passage Canal, as shown in Fig. 51, is an irregular fiord from which Port Wells, Blackstone Bay, and other branches extend. The outer portion from the entrance of Blackstone Bay and Port Wells eastward to Prince William Sound has no ice tongues whatsoever; but, as we have seen, there are numerous glaciers in the fiords that branch from it. The inner extension of Passage Canal, called Portage Bay (Fig. 51), also has ice tongues, the most conspicuous being two good-sized glaciers on the northern side, and a group of three around the western end (Fig. 54). Since none of these reach tidewater, Portage Bay is free from icebergs, excepting as they occasionally float in from Blackstone Bay or Port Wells.
Seth Glacier. This glacier, which is fed from the snowfield area from which Pigot Glacier flows eastward toward Port Wells, extends southward with a length of about 1$ miles and a width of % mile, terminating a little over a mile north of a large cove on the northern side of Passage Canal. The glacier surface is clean, with one medial moraine near the western side, and from the fiord seems to be little crevassed. Its condition previous to 1909, when Grant and Higgins mapped it from a distance, and 1910, when we saw it, is not known in sufficient detail to describe its recent history.
Neve-Sheathed Mountain Slopes. A large cirque east of Seth Glacier, and between 400 and 500 feet above sea level, contains an ice mass; and parts of the mountain slope between this cirque and Seth Glacier contain large n6 v6 fields which mantle the mountain slope, making a type of glacier similar to the thi™ sheath of ice on the slopes around the Harriman Glacier, and between glaciers around the head of Blackstone Bay. A similar n6v6 mass east of Port Wells, and just north of Esther Passage, has been given the descriptive name of Cap Glacier by Grant.
Billings Glacier—The Ice Tongue. This is the largest ice tongue in Passage Canal, having a length of over four miles and a width of about a mile. It is fed from snow-fields adjacent to those that supply Seth Glacier on the east and Harriman Glacier on the north and terminates between 1 and l£ miles from the fiord.